US and European officials are deeply sceptical that a new round of talks with Iran over its nuclear programme, opening in Moscow on Monday, will bring an end to the crisis significantly closer.

But despite public warnings from the US secretary of state, Hillary Clinton, that the negotiations must produce "concrete actions" by Tehran, western officials are grasping at small signs of progress to avoid a collapse in talks that could open the way to an Israeli military attack on Iran.

One western official involved in the talks described the last meeting between the five permanent members of the UN security council and Germany, known as the P5+1, and Iran in Baghdad last month as very difficult and was not optimistic about the next round.

"There is no trust on either side. It's hard. We need to have confidence if not trust, and confidence will also depend on clear verification of whatever steps are being taken," he said. "We're clear-eyed about this and fully expect another challenging, difficult round in Moscow. That isn't to say something can't be achieved but it's also possible there isn't much movement."

The P5+1 has told the Iranians that it is looking for a commitment from Iran to halt production of 20% enriched uranium, which is a short step from producing weapons grade, and to hand over the stockpiles it has already produced.

Clinton has said the group wants to see "concrete actions" in Moscow.

"Our negotiations with Iran have never been about intentions or sincerity but about actions and results," she said earlier this month.

"There are lots of concerns that we continue to have about their intentions but we will judge them by their actions. And we will determine whether those actions are sufficient to meet their obligations."

The western official involved with the talks said: "If the Iranians come ready to engage we are prepared to take reciprocal steps that can allow us to get some traction in this process".

But the Iranians were so short on specifics at the Baghdad talks that it's not clear even to people who were in the room what Tehran is demanding other than repeating a demand for recognition of its right to enrich uranium.

Iran has called for the lifting of tough economic sanctions but did not raise that issue in Baghdad.

"They talk around the houses," said another western official who has dealt with Iran for many years.

"They give history lessons. It's impossible to nail anything down. They build up hopes and then pull back. This is the way they've always behaved. That's why Clinton said the time has come for specifics. I wouldn't hold your breath."

The western official involved in the talks said there has been incremental progress in getting Iran to acknowledge that its uranium enrichment is the central and most immediate issue that has to be addressed.

"I can't say there's nothing there. There are things they are suggesting, engaging on. We just don't know if they're going to follow up with steps themselves. We're not just spinning our wheels," he said. "We want to see a diplomatic solution so we're committed to this process but we also need to have some level of comfort that there is going to be movement and concrete steps at the end of the day. The window of diplomacy is not indefinite."

The official said the P5+1 is looking to a new wave of US sanctions and an EU oil embargo kicking in at the end of this month to focus Tehran's attention.

"On the horizon, very near term, there's going to be increasing pressure on Iran. They know this too. Hopefully that is motivation but we do feel there is a bit of time here to continue to ratchet up pressure," he said. "It's clear to them what they need to do. We have to see what they put forward."

But scepticism still runs deep within parts of the US administration and there is open contempt for the talks from Israel which has said the P5+1 is being duped by Tehran in order to buy time.

The Israeli prime minister, Binyamin Netanyahu, accused the group of giving ground to Iran by "watering down" demands that it halt all uranium enrichment by focussing on one element, the 20% enrichment.

"In the previous round of negotiations they were asked to stop [all] enrichment but that's not what's happening now. Now they do not even insist that Iran stop all enrichment," he said. "Not only do we need to tighten the sanctions on Iran, we also need to toughen the demands from Iran and see their implementation."

Netanyahu's deputy, Moshe Yaalon, said the talks had only produced "more Iranian time-buying".

"To my regret, I don't see any sense of urgency, and perhaps it is even in the interest of some players in the west to stretch out the time, which would certainly square with the Iranian interest," he said.

The Obama administration is sensitive to charges that it is attempting to keep the negotiations rolling in order to make it difficult for Israel to attack Iran before the US election in November. But there is a tacit admission among some western officials that that is an important factor in the negotiations equation.

Obama's Republican opponent, Mitt Romney, used it to chide the president on Saturday.

"He's almost sounded like he's more frightened that Israel might take military action than he's concerned that Iran might become nuclear," he said.

But the western official involved with the talks denied it.

"We don't want talk for talks sake. We think pressure is going to continue to build on Iran," he said.

"The notion that Iran is playing for time and we're playing for time is wrong. We have a sense of urgency. We've communicated this to the Iranians, and what we're hoping is that their calculus will be affected by the bite of these sanctions. They're having a pretty significant effect on Iran's economy."